Datasheet

78K0/Ix2 CHAPTER 5 CLOCK GENERATOR
R01UH0010EJ0500 Rev.5.00 176
Feb 28, 2012
(b) To stop X1 oscillation (disabling external clock input) by setting MSTOP to 1
<1> Confirming the CPU clock status (MCM registers)
Confirm with MCS that the CPU is operating on a clock other than the internal hi-speed oscillation clock.
When MCS = 1, the high-speed system clock is supplied to the CPU, so change the CPU clock to the
internal hi-speed oscillation clock.
<2> Stopping the high-speed system clock (MOC register)
When MSTOP is set to 1, X1 oscillation is stopped (the input of the external clock is disabled).
Caution Be sure to confirm that MCS = 0 when setting MSTOP to 1. In addition, stop peripheral
hardware that is operating on the high-speed system clock.
5.6.2 Example of controlling intern
al high-speed oscillation clock
The following describes examples of clock setting procedures for the following cases.
(1) When restarting oscillation of the internal high-speed oscillation clock
(2) When using internal high-speed oscillation clock as CPU clock, and internal high-speed oscillation clock or high-
speed system clock as peripheral hardware clock
(3) When stopping the internal high-speed oscillation clock
Remark See 5.4.5 PLL (phase locked loop) when using the PLL.
(1) Example of setting procedure when restarting oscillation of the internal high-speed oscillation clock
Note 1
<1> Setting restart of oscillation of the internal high-speed oscillation clock (RCM register)
When RSTOP is cleared to 0, the internal high-speed oscillation clock starts operating.
<2> Waiting for the oscillation accuracy stabilization time of internal high-speed oscillation clock (RCM register)
Wait until RSTS is set to 1
Note 2
.
Notes 1. After a reset release, the internal high-speed oscillator automatically starts oscillating and the internal
high-speed oscillation clock is selected as the CPU clock.
2. This wait time is not necessary if high accuracy is not necessary for the CPU clock and peripheral
hardware clock.